This application claims priority of Taiwan Patent Application Serial No. 090111131 filed on May 10, 2001.
The present invention relates to a push button switch apparatus and a method of assembling the same, and more particularly, to a push button switch apparatus used in a keyboard apparatus and a method of assembling the same.
As the development of portable electronic technologies continues, engineers continually attempt to further reduce the size of such devices. In order to provide smaller keyboard devices, for example, there is a continued attempt to improve the design of push button switches used as keys in miniaturized keyboards.
FIG. 1(A) is a schematic diagram of a conventional push button switch apparatus 10. The push button switch apparatus 10 has a scissors-like structure including a key cap 11, a base plate 12, an elastically deformable actuator 13, a first arm 14, and a second arm 15. The first arm 14 and the second arm 15 are typically pivotally connected together via a pivot axle 16 so as to form the scissors-like structure of the push button switch apparatus 10. A thin film circuit board 121 is appropriately disposed on the base plate 12. A pivotal ear 123 and a bearing portion 124 are typically formed on the base plate 12.
The first arm 14 has a pivot axle 141 at its one end, and the pivot axle 141 is typically rotatably disposed in a groove 1231 of the pivotal ear 123. The second arm 15 has a pivot axle 151 at its one end, and the pivot axle 151 is slidably rotatable within a space 1241 between the bearing portion 124 and the base plate 12. The downward action of the key cap 11 causes the elastically deformable actuator 13 to downwardly press the thin film circuit board 121 to generate input signals. The scissors-like structure consists of first arm 14 and second arm 15, and functions as a holder for the deformation of the elastically deformable actuator 13 and for the up-and-down movement of the key cap 11. The thin film circuit board 121 is typically made of elastic materials, so it is regarded as a flexible layer.
Both FIG. 1(B) and FIG. 1(C) are top views of portions of elements of the push button switch apparatus 10 in FIG. 1(A) showing a method of assembling the pivot axle 141 into the groove 1231 of the pivotal ear 123. A typical scissors-like structure includes two first arms 14 connected by a shaft. Each first arm 14 typically has a U-shaped frame, as shown. Before being assembled, first arm 14 is typically pressed by a force along a direction shown as the arrowhead in FIG. 1(B), and first arm 14 is deformed to enable the pivot axle 141 to align with the groove 1231 of the pivotal ear 123. The first arm 14 is then released to make the pivot axle 141 move into the groove 1231, shown in FIG. 1(C).
Accordingly, with the design of the pivotal ear 123, the typical assembling method relies upon the deformation of the first arm 14, which results in complexity of assembly. It is therefore desirable to devise a switch structure that is assembled without the deformation of the first arm 14. Additionally, it is also desirable that a switch structure prevents the push button switch from disconnecting as the pivot axle 141 moves within the groove 1231.
In the first exemplary embodiment of the present invention, a push button switch apparatus includes a base plate and a first arm. The base plate includes a first bearing portion and a recess, wherein a pivot bearing space is formed between the base plate and the first bearing portion, and an entrance is formed on the base plate. The first arm includes a pivot axle at a first end, and the pivot axle has a protrusion. The protrusion is disposed into the recess, and the pivot axle enters into the pivot bearing space during assembly process by deforming the protrusion or the pivot axle. The walls defined by the recess constrain the pivot axle within the pivot bearing space, while the first arm selectively rotates along the pivot axle.
The second exemplary embodiment further includes a flexible layer having a second entrance on the base plate. The walls defined by the second entrance constrain the protrusion of the pivot axle and pivot axle within the pivot bearing space. One embodiment of the flexible layer is a thin film circuit board.
In the third exemplary embodiment of the present invention, the pivot axle is a short-spindle axle. By adjusting the position of the second entrance, walls defined by the second entrance constrain the protrusion of the pivot axle and pivot axle is allowed to move within the pivot bearing space.
In the fourth exemplary embodiment of the present invention, there is no protrusion on the pivot axle. The pivot axle is surrounded by the second entrance by adjusting the position of the second entrance. The pivot axle is forced into the second entrance through deformation of the shape of the second entrance. The walls defined by the second entrance constrain the pivot axle within the pivot bearing space.
In the fifth exemplary embodiment of the present invention, the pivot axle is a short-spindle axle and does not have a protrusion on the pivot axle. The walls defined by the second entrance constrain the pivot axle within the pivot bearing space.
These and other aspects of the present invention will no doubt become apparent to those of ordinary skill in the art after having read the following detailed description of the exemplary embodiments which are illustrated in the various figures and drawings.